// The NSpring Framework for .NET
// Copyright (c) 2003, Jeffrey Varszegi
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// 
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namespace NSpring.Logging {

using System;

/// <summary>
/// <para>
/// Filter instances can be used to provide filtering ability for logs on a granular
/// basis.  Filtering is useful for situations in which you may want different loggers
/// to handle different types of events; for instance, you may want a ConsoleLogger to
/// log all messages to the console, while an EmailLogger sends emails only in event
/// of an exception.
/// </para>
/// <para>
/// The NSpring.Logging.Filters package contains many predefined kinds of filters, useful
/// for filtering based on Event class properties.  For instance, the LevelFilter class
/// provides the ability to filter events based on their level.
/// </para>
/// </summary>
public abstract class Filter {
    
    protected bool isInclusive        = true;
    
    /// <summary>
    /// Indicates whether the filter is inclusive or exclusive.  If it is inclusive,
    /// any true values returned from the Matches() method will result in an Event
    /// being accepted by the filter, and vice versa; if exclusive, the opposite is true.
    /// </summary>
    public virtual bool IsInclusive {
        get {
            return isInclusive;
        }
        set {
            isInclusive = value;
        }
    }
    
    /// <summary>
    /// Indicates whether the given Event instance is accepted by this filter.  If
    /// this method returns false, the event will not be logged by any loggers using
    /// this filter.
    /// </summary>
    /// <param name="_event">The event to check for acceptability</param>
    /// <returns>true if the event is acceptable, false otherwise</returns>
    public virtual bool Accepts(Event _event) {
        if (isInclusive) {
            return Matches(_event);
        }
        else {
            return (!Matches(_event));
        }
    }
    
    /// <summary>
    /// Indicates whether the selection criteria embodied by this filter apply
    /// to the given Event instance
    /// </summary>
    /// <param name="_event">The event to check for a match</param>
    /// <returns>true if the event matches, false otherwise</returns>
    protected virtual bool Matches(Event _event) {
        return true;
    }
    
}

}
